For example, a Western style flush toilet stool is provided with a washing apparatus having a jet pipe as a feed water pipe. This jet pipe is adapted to send out the water, which flows in a feed water passage in an inner portion thereof, into storage water in a bowl portion. In this jet pipe, the air is left in a position higher than a level of the storage water when a preceding washing operation finishes. Therefore, when fresh washing water is supplied into the jet pipe by the washing apparatus so as to carry out a subsequent washing operation in this condition, the air left in the jet pipe is blown out in a lump at a stroke in a water pressure-compressed condition into the storage water, so that a comparatively large noise occurs. The same phenomenon occurs in a hot water supply apparatus and the like adapted to send out additional hot water, etc. into hot water stored in a bath tub.
Regarding the matter, JP-A-2002-106044 discloses a muffling apparatus connected to a jet pipe of a Western style flush toilet stool. This muffling apparatus includes a branch pipe diverging horizontally from the jet pipe and bent upward, a housing connected water-tightly to an upper end of this branch pipe and having at an upper end thereof a port opened in the atmospheric air, and a valve provided vertically movably in the housing and adapted to float by a buoyancy of the air and open the port of the housing. When the washing water is supplied into the jet pipe in this Western style flush toilet stool provided with this muffling apparatus, the air left in the jet pipe is introduced into the muffling apparatus, and then discharged to the atmospheric air. In short, the air left in the interior of the jet pipe is liable to be transferred to the branch pipe by a buoyancy thereof while the air is moved in the jet pipe by the water pressure, and the air transferred to the branch pipe reaches the interior of the housing. Since the valve floats in the interior of the housing owing to the air, the port of the housing is thereby opened, so that the air is discharged to the atmospheric air via the port. Thus, in the Western style flush toilet stool provided with a muffling apparatus, the air left in the interior of the jet pipe is rarely blown out into the storage water. Therefore, it is considered that the noise occurring when the air is blown out in a lump at a stroke into the storage water can be prevented.